Surgical illumination lamps generally comprise a lamp body, in the form of an enclosure closed by a transparent panel, in which at least one light source and at least one reflector, positioned in an optical relationship with the light source are mounted, for reflecting the light rays transmitted by the source in the direction of the internal surface of the housing, toward an operating field.
Illuminating lamps generally produce a round light spot at the operating field, and the maximum luminous intensity of the illumination of the operating field is obtained with a spot of diameter whose size is predetermined in accordance each type of lamp.
Surgical illuminating lamps are equipped with mechanisms for adjusting the concentration of light rays, to obtain optimal illumination of the operating field, and these mechanisms are manually actuatable.
Adjustment of the concentration is obtained by modifying the relative position of the reflector and the light source with respect to one another. Mechanisms that enable such modification are controlled by movement of a sterilizable handle that the surgeon mounts on the illuminating lamp, in its axis.
Because this handle is located in the sterile field, it cannot be mounted and manipulated by anyone but the surgeon himself or some other person working in the sterile field.
For other types of surgically illuminating lamps, adjustment of the concentration is accomplished by control buttons that are positioned outside and lateral to the lamp housing. These control buttons are located outside the sterile field, and hence they can be operated or controlled by assistants.
In the course of a surgical operation, it is often necessary to change the position of the lamp, for example in order to illuminate the operating field from another angle. This change of position, if it involves a change in the distance between the operating field illuminated and the lamp, is accompanied by an enlargement in the area illuminated, and poorer (i.e., less intense) illumination of the operating field.
The surgeon or his assistants must then readjust the concentration of the light rays manually.
In the first instance (adjustment of the concentration by the surgeon), the surgeon is obliged to interrupt his work to perform this adjustment.
In the second instance, it is not possible to obtain a precise adjustment, because the assistants have to stay outside the sterile field.